A program of studies will continue an investigation of noradrenergic and dopaminergic action on neuronal circuits in the central nervous system. Functions of the noradrenergic projection system in the cerebellum, and cerebral cortex will be examined by employing microiontophoresis of drugs, physiological activation of visual, auditory input, stimulation of locus coeruleus and use of brain slice preparations of rat. The aim will be to establish a basis for the examination of the potential interactions between the noradrenergic system and drugs of abuuse including d-amphetamine and cocaine. Similar studies will be conducted of unit activity in striatum. The proposed studies will continue exploration of the hypothesis that norepinephrine and dopamine exert a modulatory influence on synaptic efficacy, and act to regulate neuronal circuit gating functions.